Motor drive control device, electric power steering device, and vehicle

ABSTRACT

To provide a motor drive control device, an electric power steering device, and a vehicle which can individually diagnose abnormalities of magnetic detection elements, designed in a multisystem configuration to include at least two systems, for each system. A motor drive control device includes two systems of first and second rotation information detection function units. The first and second rotation information detection function units include first and second rotation position information detection units and first and second rotation information detection units. The first and second rotation information detection units individually diagnose their own abnormalities based on first and second motor rotation position signals detected by the first and second rotation position information detection units.

TECHNICAL FIELD

The present invention relates to a motor drive control device whichcontrols driving of an electric motor based on motor rotation angleinformation detected by a motor rotation sensor, and an electric powersteering device and a vehicle including the same.

BACKGROUND ART

A technology described in, for example, PTL 1 has been conventionallydisclosed to improve the reliability of the function of detecting motorrotation angle information. This technology includes two systems of amagnetic detection element and a dedicated magnetic detection element asa magnetic sensor and uses a control unit to compare pieces of angleinformation obtained therefrom, compare pieces of rotation angleinformation calculated based on angle signals, or compare pieces ofsteering position information calculated based on pieces of angleinformation, between these two systems, to diagnose the accuracy of theoutput of each magnetic detection element.

CITATION LIST Patent Literature

PTL 1: JP 2015-116964 A

SUMMARY OF INVENTION Technical Problem

However, in the technology disclosed in PTL 1, angle signals from thetwo systems of magnetic detection elements, or pieces of motor angleinformation and steering position information obtained from the anglesignals are compared with each other between the two systems to diagnosethese systems as normal for a match and as abnormal for a mismatch. Inother words, the magnetic detection elements are implemented in twosystems, while the function of diagnosing the accuracies of the anglesignals in the subsequent process, for example, are not implemented intwo systems.

Therefore, when a mismatch is found upon the occurrence of anabnormality in one of the magnetic detection elements, the magneticdetection element having the abnormality may fail to be identified, thusmaking both systems unavailable even when the other system is normal.

In view of this, the present invention has been made in consideration ofsuch a problem to be solved in the conventional technology, and has asthe object to provide a motor drive control device, an electric powersteering device, and a vehicle which can individually diagnoseabnormalities of magnetic detection elements, designed in a multisystemconfiguration to include at least two systems, for each system.

Solution to Problem

In order to solve the above problem, according to an aspect of thepresent invention, there is provided a motor drive control deviceincluding: an annular or disk-shaped magnet placed on a motor rotatingshaft of an electric motor to be rotatable in synchronism with the motorrotating shaft and includes at least two different magnetic polesarranged alternately in a circumferential direction; at least twosystems of rotation information detection function units each includinga rotation position information detection unit configured to detect amagnetic flux of the magnet which changes depending on a rotationposition of the motor rotating shaft as rotation position information, amotor rotation angle calculation unit configured to calculate a motorrotation angle based on the rotation position information detected bythe rotation position information detection unit, and a rotationposition information diagnosis unit configured to diagnose anabnormality of the rotation position information detected by therotation position information detection unit; and a motor drive controlunit configured to control driving of the electric motor based on themotor rotation angle output from the at least two systems of therotation information detection function units, wherein the rotationposition information detection unit includes a plurality of sensorelements configured to detect magnetic signals out of phase with eachother as the rotation position information, and the motor drive controlunit is configured to, when the rotation position information diagnosisunit diagnoses at least one of the at least two systems of the rotationinformation detection function units as abnormal, control driving of theelectric motor based on the motor rotation angle output from another ofthe rotation information detection function units that is normal.

In addition, in order to solve the above problem, according to anotheraspect of the present invention, there is provided an electric powersteering device including the motor drive control device describedabove.

Further, in order to solve the above problem, according to still anotheraspect of the present invention, there is provided a vehicle includingthe electric power steering device described above.

Advantageous Effects of Invention

The motor drive control device according to the present inventionincludes at least two systems of rotation information detection functionunits, each of which can diagnose an abnormality of rotation positioninformation. Therefore, when some rotation information detectionfunction units are diagnosed as abnormal, such rotation informationdetection function units having abnormalities can be identified, and theremaining normal rotation information detection function units cancontinuously control driving of the electric motor. In addition, sinceeach system is configured to detect two pieces of rotation positioninformation out of phase with each other using two sensor elements, asystem having an abnormality can be more accurately identified fromthese two pieces of rotation position information.

An electric power steering device including the above-described motordrive control device allows highly reliable steering assist control. Avehicle including the above-described electric power steering devicealso allows highly reliable steering assist control.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram illustrating the entire configuration of an electricpower steering device equipped with a motor drive control deviceaccording to a first embodiment, as applied to a vehicle;

FIG. 2 is a block diagram illustrating the entire configuration of themotor drive control device according to the first embodiment;

FIGS. 3A and 3B are views illustrating an arrangement example of a motorrotation sensor according to the first embodiment;

FIGS. 3C and 3D are views illustrating another arrangement example;

FIG. 4 is a block diagram illustrating a specific configuration exampleof rotation information detection function units according to the firstembodiment;

FIG. 5 is a waveform chart illustrating exemplary intermittent supplycontrol of a power supply control unit according to the firstembodiment;

FIG. 6 is a waveform chart illustrating exemplary variable supplycontrol of a power supply control unit according to Modification 1 ofthe first embodiment;

FIG. 7 is a block diagram illustrating an exemplary object to besupplied with power while an ignition switch for a power supply controlunit according to Modification 2 of the first embodiment is OFF;

FIG. 8 is a block diagram illustrating a specific configuration exampleof rotation information detection function units according toModification 3 of the first embodiment;

FIGS. 9A and 9B are block diagrams illustrating specific configurationexamples of a first diagnosis unit and a second diagnosis unit accordingto Modification 3 of the first embodiment;

FIG. 10A is a block diagram illustrating a specific configurationexample of a first counter unit and a first memory unit according toModification 4 of the first embodiment; and

FIG. 10B is a block diagram illustrating a specific configurationexample of a second counter unit and a second memory unit according toModification 4 of the first embodiment.

DESCRIPTION OF EMBODIMENTS

A first embodiment and Modifications 1 to 4 of the present inventionwill be described below with reference to the drawings. In the followingdrawings, the same or similar reference numerals denote the same orsimilar parts. However, it should be noted that the drawings includeschematic representations, and the vertical and horizontal sizes orscales of members or parts may be different from the actual ones.Accordingly, specific sizes or scales should sometimes be determined inconsideration of the following description. The respective drawingsinclude parts having different size relationships or ratios, as a matterof course.

The following first embodiment and Modifications 1 to 4 exemplifydevices or methods for embodying the technical idea of the presentinvention, and the technical idea of the present invention does notlimit, for example, the materials, shapes, structures, and arrangementsof components to the following specific examples. Various changes can bemade to the technical idea of the present invention within the technicalscope defined by claims described in the scope of claims.

First Embodiment

(Entire Configuration)

A vehicle 1 according to a first embodiment includes front wheels 4FRand 4FL serving as left and right steered wheels, and rear wheels 4RRand 4RL, as illustrated in FIG. 1. The front wheels 4FR and 4FL areturned by an electric power steering device 3.

The electric power steering device 3 includes a steering wheel 31, asteering shaft 32, a first universal joint 34, a lower shaft 35, and asecond universal joint 36.

The electric power steering device 3 further includes a pinion shaft 37,a steering gear 38, tie rods 39, knuckle arms 40, and a torque sensor41.

A steering force acting on the steering wheel 31 as the driver operatesis transmitted to the steering shaft 32. The steering shaft 32 includesan input shaft 32 a and an output shaft 32 b. The input shaft 32 a hasone end connected to the steering wheel 31, and the other end connectedto one end of the output shaft 32 b via the torque sensor 41.

The steering force transmitted to the output shaft 32 b is transmittedto the lower shaft 35 via the first universal joint 34 and further tothe pinion shaft 37 via the second universal joint 36. The steeringforce transmitted to the pinion shaft 37 is transmitted to the tie rods39 via the steering gear 38. The steering force transmitted to the tierods 39 is further transmitted to the knuckle arms 40 to turn the frontwheels 4FR and 4FL.

The steering gear 38 employs a rack-and-pinion system including a pinion38 a connected to the pinion shaft 37 and a rack 38 b which meshes withthe pinion 38 a. Therefore, the steering gear 38 converts a rotationalmotion transmitted to the pinion 38 a into a rectilinear motion in thevehicle widthwise direction in the rack 38 b.

The torque sensor 41 detects a steering torque T applied to the steeringwheel 31 and transmitted to the input shaft 32 a.

A steering assist mechanism 42 which transmits a steering assist forceto the output shaft 32 b of the steering shaft 32 is connected to theoutput shaft 32 b.

The steering assist mechanism 42 includes a reduction gear 43implemented in a worm gear mechanism connected to the output shaft 32 b,an electric motor 44 which is connected to the reduction gear 43 andgenerates a steering assist force, and a motor drive control device 45fixed and supported on the housing of the electric motor 44.

The electric motor 44 is implemented as a three-phase brushless motorand includes an annular motor rotor and an annular motor stator (neitheris illustrated). The motor stator includes a plurality ofcircumferentially equidistant pole teeth projecting radially inwards,and a magnetic exciting coil is wound around each pole tooth. The motorrotor is coaxially placed inside the motor stator. The motor rotorincludes a plurality of circumferentially equidistant magnets arrangedon its outer peripheral surface and opposed to the pole teeth of themotor stator with slight air gaps between them.

The motor rotor is fixed to a motor rotating shaft and rotates uponmagnetic excitation of the teeth of the motor stator in a predeterminedsequence by supplying a three-phase AC current to the coil of the motorstator via the motor drive control device 45, and the motor rotatingshaft rotates with this rotation.

When the motor rotating shaft rotates, its rotational force (steeringassist force) is transmitted to the steering shaft 32 via the reductiongear 43 to rotate the steering shaft 32. When the steering wheel 31 issteered to rotate the steering shaft 32, its rotational force istransmitted to the motor rotating shaft via the reduction gear 43 torotate the motor rotor. In other words, since the rotation positions ofthe electric motor 44 and the steering shaft 32 have a correspondence,the rotation position of one of them can be calculated from the rotationinformation of the other.

The motor drive control device 45 is actuated upon being supplied withpower from a battery 61 serving as a vehicle-mounted power supply. Thebattery 61 has its anode connected to ground and its cathode connectedto the motor drive control device 45 via an ignition switch 62 (to bealso referred to as the “IG switch 62” hereinafter) which starts anengine and directly connected to the motor drive control device 45without the IG switch 62.

The motor drive control device 45 receives the steering torque Tdetected by the torque sensor 41, and a vehicle speed V detected by avehicle speed sensor 60, as illustrated in FIG. 1.

(Configuration of Motor Drive Control Device 45)

The motor drive control device 45 includes a motor rotation sensor 46, arotation detector 47, a controller 48, a motor drive circuit 49, and apower supply control unit 50, as illustrated in FIG. 2.

The motor rotation sensor 46 is implemented as a magnetic sensor fordetecting rotation position information of the electric motor 44 andincludes a first rotation position information detection unit 46 b and asecond rotation position information detection unit 46 c as two systemsof rotation position information detection units, as illustrated inFIGS. 3A to 3D. The detailed arrangement of the motor rotation sensor 46will be described later.

Referring back to FIG. 2, the rotation detector 47 receives a firstmotor rotation position signal (sin θ1, cos θ1) and a second motorrotation position signal (sin θ2, cos θ2) as magnetic detection signalsdetected by the first and second rotation position information detectionunits 46 b and 46 c.

The first motor rotation position signal (sin θ1, cos θ1) and the secondmotor rotation position signal (sin θ2, cos θ2) will also be abbreviatedindividually as “sin θ1”, “cos θ1”, “sin θ2” and “cos θ2” hereinafter.

The rotation detector 47 includes two systems of a first and a secondrotation information detection units 47 a and 47 b which performprocessing for diagnosing abnormalities of the input first motorrotation position signal (sin θ1, cos θ1) and second motor rotationposition signal (sin θ2, cos θ2), that for calculating a motor rotationangle θm, that for measuring an amount of change in motor rotationposition, and the like, based on these motor rotation position signals,as illustrated in FIG. 4. The detailed configuration of the rotationdetector 47 will be described later.

The rotation detector 47 according to the first embodiment is configuredto continue processing for measuring an amount of change in motorrotation position even while the IG switch 62 is OFF, although detailswill be described later.

Referring back to FIG. 2, the controller 48 controls the motor drivecircuit 49 based on the steering torque T, the vehicle speed V, and themotor rotation angle θm and the amount of change in motor rotationposition (count values Cs and Cc; to be described later) from therotation detector 47 to control driving of the electric motor 44.

More specifically, in steering assist control, the controller 48calculates a steering assist command value (steering assist torquecommand value) for generating a steering assist torque according to thesteering torque T, the vehicle speed V, and the motor rotation angle θmin the electric motor 44, using a known procedure, and, in turn,calculates a first current command value Iref1 for steering assistcontrol based on the calculated steering assist command value. Thecontroller 48 controls the motor drive circuit 49 based on thecalculated first current command value Iref1 to control driving of theelectric motor 44.

In this case, the controller 48 according to the first embodimentdetermines whether or not an abnormality has occurred in the first motorrotation position signal (sin θ1, cos θ1) and the second motor rotationposition signal (sin θ2, cos θ2), based on the respective abnormalitydiagnosis results obtained by the two systems of a first and a secondrotation information detection units 47 a and 47 b of the rotationdetector 47. When the controller 48 determines that an abnormality hasoccurred in one of these signals, it performs steering assist controlbased on a motor rotation angle having no abnormality of a first motorrotation angle θm1 calculated based on the first motor rotation positionsignal (sin θ1, cos θ1) and a second motor rotation angle θm2 calculatedbased on the second motor rotation position signal (sin θ2, cos θ2).

The controller 48 calculates (estimates) the rotation position θs (to bealso referred to as the “steering angle θs” hereinafter) of the steeringshaft 31 based on the motor rotation angle θm from the rotation detector47 while the IG switch 62 is ON.

However, when the IG switch 62 changes from OFF to ON, the controller 48according to the first embodiment calculates a steering angle θs upon achange from OFF to ON, based on the steering angle θs and the amount ofchange in motor rotation position (count values Cs and Cc; to bedescribed later) immediately before switch-off stored in a nonvolatilememory (not illustrated) in advance, and the amount of change in motorrotation position immediately after switch-on.

In performing autonomous cruise control in accordance with a commandfrom an autonomous cruise controller (not illustrated), the controller48 calculates a second current command value Iref2 for autonomous cruisecontrol based on a target steering angle θs* from the autonomous cruisecontroller, the calculated steering angle θs, and the motor rotationangle θm from the rotation detector 47. The controller 48 controls themotor drive circuit 49 based on the calculated second current commandvalue Iref2 to control driving of the electric motor 44.

The motor drive circuit 49 includes a three-phase inverter circuit (notillustrated) and drives the three-phase inverter circuit based on adrive signal (for example, a PWM signal) from the controller 48 tosupply a motor drive current to the electric motor 44.

The power supply control unit 50 is connected to the battery 61 directlyand to the IG switch 62 and receives a signal (to be also referred to asan “IG signal” or “IG” hereinafter) indicating ON and OFF of the IGswitch 62 from the IG switch 62. When the power supply control unit 50determines that the IG switch 62 is ON based on the input IG signal, itcontinuously supplies power from the battery 61 to the first and secondrotation position information detection units 46 b and 46 c and therotation detector 47 in ON state.

The power supply state in which power is continuously supplied from thebattery 61 will also be referred to as the “normally supplied state”hereinafter.

When the power supply control unit 50 determines that the IG switch 62is OFF, it intermittently supplies power from the battery 61 to thefirst and second rotation position information detection units 46 b and46 c and the rotation detector 47 at a preset certain interval in OFFstate. In other words, the power supply control unit 50 is configured toreduce the power consumption while the IG switch is OFF by intermittentsupply.

The power supply state in which power is intermittently supplied fromthe battery 61 will also be referred to as the “intermittently suppliedstate” hereinafter.

The certain interval value in intermittent supply is determined from thecapacity (dark current) of the battery 61 and the maximum rotationalspeed of the steering wheel 31. In other words, since a change in motorrotation position may fail to be followed when the interval at which nopower is supplied is set too long, the interval is determined to allowsufficient following.

(Arrangement of Motor Rotation Sensor 46)

The specific arrangement of the motor rotation sensor 46 will bedescribed below with reference to FIGS. 3A to 3D.

The motor rotation sensor 46 according to the first embodiment is placedat the stator end position, on the side of the reduction gear 43, of amotor rotating shaft 44 a located in a motor stator for the electricmotor 44, as illustrated in FIG. 3A.

More specifically, the motor rotation sensor 46 includes a multipolarring magnet 46 a, a first rotation position information detection unit46 b, and a second rotation position information detection unit 46 c, asillustrated in FIG. 3B.

The multipolar ring magnet 46 a is implemented as an annular(ring-shaped) multipolar magnet magnetized with its south and northpoles circumferentially alternately arranged on the outer surface insequence and is fixed and supported on the motor rotating shaft 44 a.The multipolar ring magnet 46 a is fixed and supported to be rotatablein synchronism with the motor rotating shaft 44 a inside the motorstator concentrically with the motor rotating shaft 44 a as the motorrotating shaft 44 a is inserted into its central through hole. Thisrotates the multipolar ring magnet 46 a in synchronism with rotation ofthe motor rotating shaft 44 a.

The multipolar ring magnet 46 a is magnetized by sinusoidalmagnetization and has a sinusoidal magnetic flux density distribution oneach magnetic pole surface.

The first rotation position information detection unit 46 b includes afirst magnetic detection element 46 d and a second magnetic detectionelement 46 e. The first magnetic detection element 46 d and the secondmagnetic detection element 46 e are opposed to the outer peripheralsurface of the multipolar ring magnet 46 a with a given spacing betweenthem and juxtaposed to each other to be out of phase with each other byan electrical angle of 90° in the circumferential direction of themultipolar ring magnet 46 a.

The second rotation position information detection unit 46 c includes athird magnetic detection element 46 f and a fourth magnetic detectionelement 46 g. The third magnetic detection element 46 f and the fourthmagnetic detection element 46 g are opposed to the outer peripheralsurface of the multipolar ring magnet 46 a with a given spacing betweenthem and juxtaposed to each other to be out of phase with each other byan electrical angle of 90° in the circumferential direction of themultipolar ring magnet 46 a.

With such an arrangement, the first rotation position informationdetection unit 46 b can detect a magnetic flux of the multipolar ringmagnet 46 a which changes depending on the rotation position of themotor rotating shaft 44 a as a sine and cosine wave magnetic detectionsignal (first motor rotation position signal (sin θ1, cos θ1)). Thesecond rotation position information detection unit 46 c can detect amagnetic flux of the multipolar ring magnet 46 a which changes dependingon the rotation position of the motor rotating shaft 44 a as a sine andcosine wave magnetic detection signal (second motor rotation positionsignal (sin θ2, cos θ2)). The first motor rotation position signal (sinθ1, cos θ1) and the second motor rotation position signal (sin θ2, cosθ2) match each other when the first rotation position informationdetection unit 46 b and the second rotation position informationdetection unit 46 c are normal.

In other words, the motor rotation sensor 46 according to the firstembodiment includes two systems of rotation position informationdetection units.

The motor rotation sensor 46 illustrated in FIGS. 3A and 3B is designedby opposing the first rotation position information detection unit 46 band the second rotation position information detection unit 46 c to theouter peripheral surface of the multipolar ring magnet 46 a with a givenspacing between them, but the present invention is not limited to thisarrangement.

As illustrated as, for example, a motor rotation sensor 46′ in FIG. 3C,the first rotation position information detection unit 46 b and thesecond rotation position information detection unit 46 c may be opposedto the axial end surface of the multipolar ring magnet 46 a with a givenspacing between them.

The motor rotation sensor is not limited to the arrangements illustratedin FIGS. 3A to 3C, and a motor rotation sensor 53 illustrated in FIG.3D, for example, may be used.

The motor rotation sensor 53 includes a bipolar magnet 53 a and a thirdrotation position information detection unit 53 b.

The bipolar magnet 53 a is implemented as a disk-shaped magnet with oneaxial end surface magnetized to two poles: the south and north poles andis fixed and supported on the motor rotating shaft 44 a as the end ofthe motor rotating shaft 44 a opposite to the reduction gear 43 isinserted concentrically with the bipolar magnet 53 a into a recessformed at the center of the surface opposite to the magnetized surface.This rotates the bipolar magnet 53 a in synchronism with rotation of themotor rotating shaft 44 a.

The third rotation position information detection unit 53 b is opposedto the other axial end surface of the bipolar magnet 53 a with a givenspacing between them. The third rotation position information detectionunit 53 b includes two systems of rotation position informationdetection units (not illustrated), like the motor rotation sensor 46,and can detect a first motor rotation position signal (sin θ1, cos θ1)and a second motor rotation position signal (sin θ2, cos θ2), like themotor rotation sensor 46 again.

(Configuration of Rotation Detector 47)

The specific configuration of the rotation detector 47 will be describedbelow with reference to FIG. 4.

The rotation detector 47 includes a first rotation information detectionunit 47 a and a second rotation information detection unit 47 b, asillustrated in FIG. 4.

The first rotation position information detection unit 46 b and thefirst rotation information detection unit 47 a form a first rotationinformation detection function unit 51, and the second rotation positioninformation detection unit 46 c and the second rotation informationdetection unit 47 b form a second rotation information detectionfunction unit 52. In other words, the motor drive control device 45according to the first embodiment includes two systems of rotationinformation detection function units.

The first rotation information detection unit 47 a includes a first ADC(Analog-to-Digital Converter) 471 a, a first diagnosis unit 471 b, afirst counter unit 471 c, a first memory unit 471 d, a first rotationangle calculation unit 471 e, and a first output determination unit 471f.

When the first ADC 471 a receives an analog, first motor rotationposition signal (sin θ1, cos θ1) from the first rotation positioninformation detection unit 46 b, it converts the signal into a firstdigital rotation position signal (sin θd1, cos θd1) as a digital, firstmotor rotation position signal. The first ADC 471 a outputs the firstdigital rotation position signal (sin θd1, cos θd1) to each of the firstdiagnosis unit 471 b, the first counter unit 471 c, and the firstrotation angle calculation unit 471 e.

The first digital rotation position signal (sin θd1, cos θd1) will alsobe abbreviated simply as a “first digital rotation position signal” orindividually as “sin θd1” and “cos θd1” hereinafter.

The first diagnosis unit 471 b diagnoses an abnormality of the firstdigital rotation position signal, based on this first digital rotationposition signal. The first diagnosis unit 471 b sets a first diagnosisresult flag DR1 indicating the diagnosis result and outputs the firstdiagnosis result flag DR1 to each of the first counter unit 471 c, thefirst memory unit 471 d, and the first output determination unit 471 f.

More specifically, the first diagnosis unit 471 b diagnoses anabnormality of the first digital rotation position signal based on thefollowing equation (1):sin θd ²+cos θd ²=1  (1)

In other words, calculating the squares of sin and cos signals yieldswaveforms that are identical, but opposite in phase, and equation (1)holds. Accordingly, as long as sin θd1 and cos θd1 are normal, the sumof their squares “sin θd1 ²+cos θd1 ²” is 1.

As long as the sum of the squares of sin θd1 and cos θd1 is 1, the firstdigital rotation position signal can be diagnosed as having noabnormality (as normal). The signal can be diagnosed as abnormal when anumerical value other than “1” is set.

The first diagnosis unit 471 b sets the first diagnosis result flag DR1to “0” when the signal is diagnosed as normal and to “1” when the signalis diagnosed as abnormal.

The first counter unit 471 c counts the values of sin θd1 and cos θd1for each of their quadrants and outputs a first sin count value Cs1 anda first cos count value Cc1 to the first memory unit 471 d as the countvalues.

The first sin count value Cs1 and the first cos count value Cc1 willalso be abbreviated as the “first count values Cs1 and Cc1” hereinafter.

The first counter unit 471 c is configured to stop the operation whenthe first diagnosis result flag DR1 input from the first diagnosis unit471 b is “1”.

Since the first counter unit 471 c has a design count set per cycle,rotation count information can also be evaluated based on the firstcount values Cs1 and Cc1.

The first memory unit 471 d includes a nonvolatile memory (notillustrated) and stores the first count values Cs1 and Cc1 input fromthe first counter unit 471 c in the nonvolatile memory.

The first memory unit 471 d is configured to stop the operation when thefirst diagnosis result flag DR1 input from the first diagnosis unit 471b is “1.”

The first rotation angle calculation unit 471 e calculates a first motorrotation angle θm1 based on the first digital rotation position signalfrom the first ADC 471 a. The first rotation angle calculation unit 471e outputs the calculated first motor rotation angle θm1 to the firstoutput determination unit 471 f.

The first output determination unit 471 f outputs the first diagnosisresult flag DR1 input from the first diagnosis unit 471 b and the firstmotor rotation angle θm1 input from the first rotation angle calculationunit 471 e to the controller 48 when the first diagnosis result flag DR1is “0.” When the IG switch 62 changes from OFF to ON, the first outputdetermination unit 471 f further outputs the first count values Cs1 andCc1 stored in the first memory unit 471 d to the controller 48.

The first output determination unit 471 f stops outputting the firstmotor rotation angle θm1 and the first count values Cs1 and Cc1 andoutputs only the first diagnosis result flag DR1 to the controller 48,when the first diagnosis result flag DR1 is “1.”

The second rotation information detection unit 47 b includes a secondADC 472 a, a second diagnosis unit 472 b, a second counter unit 472 c, asecond memory unit 472 d, a second rotation angle calculation unit 472e, and a second output determination unit 472 f.

When the second ADC 472 a receives an analog, second motor rotationposition signal (sin θ2, cos θ2) from the second rotation positioninformation detection unit 46 c, it converts the signal into a seconddigital rotation position signal (sin θd2, cos θd2) as a digital, secondmotor rotation position signal. The second ADC 472 a outputs the seconddigital rotation position signal (sin θd2, cos θd2) to each of thesecond diagnosis unit 472 b, the second counter unit 472 c, and thesecond rotation angle calculation unit 472 e.

The second digital rotation position signal (sin θd2, cos θd2) will alsobe abbreviated simply as a “second digital rotation position signal” orindividually as “sin θd2” and “cos θd2” hereinafter.

The second diagnosis unit 472 b, the second counter unit 472 c, thesecond memory unit 472 d, the second rotation angle calculation unit 472e, and the second output determination unit 472 f perform the sameoperations as those of the first diagnosis unit 471 b, the first counterunit 471 c, the first memory unit 471 d, the first rotation anglecalculation unit 471 e, and the first output determination unit 471 f,respectively, except that different signals are used. Hence, these unitswill not be described herein.

A flag indicating the diagnosis result obtained by the second diagnosisunit 472 b is defined as a second diagnosis result flag DR2, the countvalues obtained by the second counter unit 472 c are defined as a secondsin count value Cs2 and a second cos count value Cc2, and the motorrotation angle calculated by the second rotation angle calculation unit472 e is defined as a second motor rotation angle θm2.

The second sin count value Cs2 and the second cos count value Cc2 willalso be abbreviated as the “second count values Cs2 and Cc2”hereinafter.

With the above-mentioned configuration of the first and second rotationinformation detection function units 51 and 52, the controller 48 canrecognize that an abnormality has occurred in the first rotationinformation detection function unit 51 when the first diagnosis resultflag DR1 is “1,” and recognize that an abnormality has occurred in thesecond rotation information detection function unit 52 when the seconddiagnosis result flag DR2 is “1.” In other words, one of the first andsecond rotation information detection function units 51 and 52, havingan abnormality, can be identified.

The controller 48 according to the first embodiment is configured to,upon detection of an abnormality, notify the driver of the abnormalityby turning on a warning lamp (not illustrated) and displaying a warningmessage on a display of a car navigation system (not illustrated).

The first rotation information detection unit 47 a and the secondrotation information detection unit 47 b according to the firstembodiment are independent of each other. These units are formedindependently of each other by a circuit such as an ASIC (ApplicationSpecific Integrated Circuit) that is an integrated circuit designed andmanufactured for any specific application, or an FPGA (FieldProgrammable Gate Array) that is an integrated circuit whoseconfiguration can be set by a purchaser or a designer after manufacture.Therefore, even when an abnormality occurs in one of these units, theother unit can be independently operated free from the influence of theabnormality.

The first and second rotation information detection function units 51and 52 according to the first embodiment are intermittently suppliedwith power from the battery 61 via the power supply control unit 50 evenwhen the IG switch 62 is turned off. The first and second rotationinformation detection function units 51 and 52 can, therefore, continueprocessing for detecting a first and a second motor rotation positionsignals, that for A/D-converting the first and second motor rotationposition signals, that for counting a first and a second digitalrotation position signals, and that for storing the count values, evenwhile the IG switch 62 is OFF.

With this operation, even when the steering wheel 31 is steered whilethe IG switch 62 is OFF, a change in motor rotation position can befollowed, and the controller 48 can calculate an accurate steering angleθs based on the first count values Cs1 and Cc1 and the second countvalues Cs2 and Cc2 input from the first rotation information detectionfunction unit 51 and the second rotation information detection functionunit 52 when the IG switch 62 changes from OFF to ON.

(Operation)

An operation according to the first embodiment will be described belowwith reference to FIG. 5.

Assume now that the IG switch 62 is ON, and power is supplied from thebattery 61 to the first and second rotation information detectionfunction units 51 and 52 via the power supply control unit 50 in thenormally supplied state.

In this state, the first and second rotation position informationdetection units 46 b and 46 c detect the first and second motor rotationposition signals according to the motor rotation position, and input thedetected first and second motor rotation position signals to the firstand second rotation information detection units 47 a and 47 b.

With this operation, the first and second rotation information detectionunits 47 a and 47 b use the first and second ADCs 471 a and 472 a toconvert the input an analog, first and second motor rotation positionsignals into the digital, first and second digital rotation positionsignals. The first and second rotation information detection units 47 aand 47 b output the first and second digital rotation position signalsafter conversion to each of the first and second diagnosis units 471 band 472 b, the first and second counter units 471 c and 472 c, and thefirst and second rotation angle calculation units 471 e and 472 e.

The first and second diagnosis units 471 b and 472 b calculate “sin θd1²+cos θd1 ²” and “sin θd2 ²+cos θd2 ²” in accordance with equation (1)from the input first and second digital rotation position signals anddetermine whether or not their calculation results are “1”.

Assuming herein that the calculation results are both “1”, the first andsecond diagnosis units 471 b and 472 b output “0” as the first andsecond diagnosis result flags DR1 and DR2 to each of the first andsecond counter units 471 c and 472 c, the first and second memory units471 d and 472 d, and the first and second output determination units 471f and 472 f.

The first and second counter units 471 c and 472 c count the input firstand second digital rotation position signals for each quadrant andoutput, as their count values, the first count values Cs1 and Cc1 to thefirst memory unit 471 d and the second count values Cs2 and Cc2 to thesecond memory unit 472 d.

The first memory unit 471 d stores the input first count values Cs1 andCc1 in its own nonvolatile memory, and the second memory unit 472 dstores the input second count values Cs2 and Cc2 in its own nonvolatilememory.

The first and second rotation angle calculation units 471 e and 472 ecalculate a first and a second motor rotation angles θm1 and θm2 fromthe input first and second digital rotation position signals and outputthe first motor rotation angle θm1 to the first output determinationunit 471 f and the second motor rotation angle θm2 to the second outputdetermination unit 472 f.

The first and second output determination units 471 f and 472 f outputthe input first and second diagnosis result flags DR1 and DR2 and theinput first and second motor rotation angles θm1 and θm2 to thecontroller 48, because these first and second diagnosis result flags DR1and DR2 are “0”.

The controller 48 determines that no abnormality has occurred in boththe first and second rotation information detection function units 51and 52 (both of these units are normal), based on the first and seconddiagnosis result flags DR1 and DR2 input from the first and secondrotation information detection function units 51 and 52.

The controller 48 calculates a steering angle θs based on the firstmotor rotation angle θm1 in this case, of the input first and secondmotor rotation angles θm1 and θm2. The controller 48 controls driving ofthe electric motor 44 based on the first motor rotation angle θm1 insteering assist control and controls driving of the electric motor 44based on the calculated steering angle θs and the first motor rotationangle θm1 in autonomous cruise control.

When the IG switch 62 is turned off, the power supply control unit 50switches the state of power supply from the battery 61 to the first andsecond rotation information detection function units 51 and 52 from thenormally supplied state to the intermittently supplied state.

More specifically, a switch (not illustrated) for switching between ONand OFF of power supplied from the battery 61 to the first and secondrotation information detection function units 51 and 52 is alternatelyturned on and off at certain intervals respectively set in advance forON and OFF states (1 [ms] in the example of FIG. 5), as illustrated inFIG. 5. Note that power is supplied when the switch is ON, and no poweris supplied when the switch is OFF.

Even in the intermittently supplied state, the analog, first and secondmotor rotation position signals are input to the first and second ADCs471 a and 472 a and converted into the digital, first and second digitalrotation position signals. The first and second diagnosis units 471 band 472 b diagnose the first and second digital rotation positionsignals. The first and second rotation angle calculation units 471 e and472 e perform processing for calculating the first and second motorrotation angles θm1 and θm2.

Assume herein that the first and second digital rotation positionsignals have no abnormalities, and the first and second diagnosis resultflags DR1 and DR2 become “0”.

Then, even in the intermittently supplied state, the first and secondcounter units 471 c and 472 c continue their counting processing, andthe first and second memory units 471 d and 472 d continue processingfor storing the count values.

In this case, assume, for example, that the driver riding in a vehicle 1equipped with the so-called idling stop function of automaticallystopping an engine at the time of stoppage steers the steering wheel 31to rotate the motor rotating shaft 44 a after the IG switch 62 is turnedoff by this idling stop function, while waiting for the lights tochange.

In this manner, even when steering is performed while the IG switch 62is OFF, the first and second counter units 471 c and 472 c can countvalues according to changes of the first and second digital rotationposition signals, and the first memory unit 471 d and the second memoryunit 472 d can store the first count values Cs1 and Cc1 and the secondcount values Cs2 and Cc2.

When the IG switch 62 changes from OFF to ON, the first and secondoutput determination units 471 f and 472 f output not only the first andsecond diagnosis result flags DR1 and DR2 and the first and second motorrotation angles θm1 and θm2, but also the first count values Cs1 and Cc1and the second count values Cs2 and Cc2 stored in the first and secondmemory units 471 d and 472 d to the controller 48.

The controller 48 calculates a steering angle θs based on the inputfirst count values Cs1 and Cc1 and second count values Cs2 and Cc2 andcontrols driving of the electric motor 44 based on the calculatedsteering angle θs and the input first and second motor rotation anglesθm1 and θm2 in autonomous cruise control.

Assume that the same processing as in the above-mentioned normal supplyis performed in the normally supplied state, and the first diagnosisresult flag DR1 becomes “1” and the second diagnosis result flag DR2becomes “0” in the first and second diagnosis units 471 b and 472 b. Inother words, assume that “1” as the first diagnosis result flag DR1indicating an abnormality is input to the first counter unit 471 c, thefirst memory unit 471 d, and the first output determination unit 471 f.

Then, the first counter unit 471 c and the first memory unit 471 d stoptheir operations.

The first output determination unit 471 f stops outputting the firstmotor rotation angle θm1 and the first count values Cs1 and Cc1 andoutputs only the first diagnosis result flag DR1 (=1) to the controller48.

The second rotation information detection function unit 52 normallyoperates to output the second diagnosis result flag DR2 (=0) and thesecond motor rotation angle θm2 to the controller 48.

The controller 48 determines that an abnormality has occurred in thefirst rotation information detection function unit 51 from the inputfirst diagnosis result flag DR1 (=1) and determines that the secondrotation information detection function unit 52 is normal from the inputsecond diagnosis result flag DR2 (=0). The controller 48 controlsdriving of the electric motor 44 using the second motor rotation angleθm2 input from the second rotation information detection function unit52 determined to be normal.

The multipolar ring magnet 46 a corresponds to an annular magnet, thefirst and second rotation position information detection units 46 b and46 c correspond to a rotation position information detection unit, andthe first and second rotation angle calculation units 471 e and 472 ecorrespond to a motor rotation angle calculation unit.

The first and second diagnosis units 471 b and 472 b correspond to arotation position information diagnosis unit, the controller 48 and themotor drive circuit 49 correspond to a motor drive control unit, and thefirst and second rotation information detection function units 51 and 52correspond to at least two systems of rotation information detectionfunction units.

The first and second counter units 471 c and 472 c and the first andsecond memory units 471 d and 472 d correspond to a rotation changeamount measurement unit.

Effects of First Embodiment

(1) The motor drive control device 45 according to the first embodimentincludes an annular multipolar ring magnet 46 a that is placed on themotor rotating shaft 44 a of the electric motor 44 to be rotatable insynchronism with the motor rotating shaft 44 a and has at least twodifferent magnetic poles circumferentially alternately arranged.

The motor drive control device 45 further includes two systems ofrotation information detection function units: a first rotationinformation detection function unit 51 and a second rotation informationdetection function unit 52. The first rotation information detectionfunction unit 51 includes a first rotation position informationdetection unit 46 b which detects a magnetic flux of the multipolar ringmagnet 46 a which changes depending on the rotation position of themotor rotating shaft 44 a, that is, magnetic detection signals out ofphase with each other by an electrical angle of 90° as rotation positioninformation (first motor rotation position signal (sin θ1, cos θ1))using the first magnetic detection element 46 d and the second magneticdetection element 46 e, a first rotation angle calculation unit 471 ewhich calculates a first motor rotation angle θm1 based on the rotationposition information detected by the first rotation position informationdetection unit 46 b, and a first diagnosis unit 471 b which diagnoses anabnormality of the rotation position information detected by the firstrotation position information detection unit 46 b. The second rotationinformation detection function unit 52 includes a second rotationposition information detection unit 46 c which detects a magnetic fluxof the multipolar ring magnet 46 a which changes depending on therotation position of the motor rotating shaft 44 a, that is, magneticdetection signals out of phase with each other by an electrical angle of90° as rotation position information (second motor rotation positionsignal (sin θ2, cos θ2)) using the third magnetic detection element 46 fand the fourth magnetic detection element 46 g, a second rotation anglecalculation unit 472 e which calculates a second motor rotation angleθm2 based on the rotation position information detected by the secondrotation position information detection unit 46 c, and a seconddiagnosis unit 472 b which diagnoses an abnormality of the rotationposition information detected by the second rotation positioninformation detection unit 46 c.

The motor drive control device 45 further includes a controller 48 and amotor drive circuit 49 which control driving of the electric motor 44based on the first and second motor rotation angles θm1 and θm2 outputfrom the two systems of the first and second rotation informationdetection function units 51 and 52.

When one of the first and second rotation information detection functionunits 51 and 52 diagnoses an abnormality of the motor rotation positionsignal thereof, the controller 48 and the motor drive circuit 49 controldriving of the electric motor 44 based on the motor rotation angleoutput from the other, normal rotation information detection functionunit.

With this configuration, since the first and second rotation informationdetection function units 51 and 52, each of which can diagnose anabnormality of rotation position information thereof, are used, therotation information detection function unit having an abnormality canbe identified, and when one rotation information detection function unitdiagnoses an abnormality, drive control of the electric motor 44 can becontinued by using the other, normal rotation information detectionfunction unit. In addition, since each system is configured to detecttwo pieces of rotation position information (sin θ, cos θ) 90° out ofphase with each other using two magnetic detection elements, a systemhaving an abnormality can be more accurately identified from these twopieces of rotation position information.

(2) In the motor drive control device 45 according to the firstembodiment, the electric motor 44 serves as a motor which applies asteering assist force to the steering shaft 32 of the vehicle 1 equippedwith the motor drive control device 45, and the first and secondrotation information detection function units 51 and 52 include thefirst and second counter units 471 c and 472 c and the first and secondmemory units 471 d and 472 d which measure an amount of change inrotation position of the electric motor 44.

The motor drive control device 45 is further configured to supply powerfrom the battery 61 of the vehicle 1 to the first and second rotationinformation detection function units 51 and 52 even while the IG switch62 is OFF, and the first and second counter units 471 c and 472 c andthe first and second memory units 471 d and 472 d continuously measureand store an amount of change in rotation position even while the IGswitch 62 is OFF.

The controller 48 and the motor drive circuit 49 calculate a steeringangle θs that is the rotation angle of the steering shaft 32 based onthe amount of change in motor rotation position measured by the firstand second counter units 471 c and 472 c and the first and second memoryunits 471 d and 472 d when the IG switch 62 changes from OFF to ON, andfurther calculate a steering angle θs based on the first and secondmotor rotation angles θm1 and θm2 while the IG switch 62 is subsequentlykept ON, to control driving of the electric motor 44 based on thecalculated steering angle θs.

With this configuration, even when the driver of the vehicle 1 steersthe steering wheel 31 while the IG switch 62 is OFF, an amount of changein motor rotation position can be continuously measured. This can yieldan accurate steering angle θs from the measured amount of change,immediately after the IG switch 62 changes from OFF to ON. As a result,a measure can be immediately taken upon control including steering anglecontrol such as autonomous cruise control directly after ON state isset.

(3) The motor drive control device 45 according to the first embodimentincludes a power supply control unit 50 which intermittently suppliespower from the battery 61 of the vehicle 1 to the first and secondrotation information detection function units 51 and 52 while the IGswitch 62 is OFF.

With this configuration, the first and second rotation informationdetection function units 51 and 52 can be continuously operated evenwhile the IG switch 62 is OFF, and the power consumption in OFF statecan be cut.

(4) The electric power steering device 3 according to the firstembodiment includes the motor drive control device 45. The vehicle 1according to the first embodiment includes the electric power steeringdevice 3.

Both arrangements thus allow highly reliable steering assist control.

Modification 1 of First Embodiment

Modification 1 of the first embodiment will be described below withreference to FIG. 6.

Modification 1 is different from the first embodiment in that in thefirst embodiment the power supply control unit 50 intermittentlysupplies power from the battery 61 at a certain interval to allconstituent units of the first and second rotation information detectionfunction units 51 and 52 while the IG switch 62 is OFF, but inModification 1 the interval at which power is supplied is changed.

The same reference numerals as in the first embodiment denote the sameconstituent units, and a description thereof will be omitted asappropriate, while only different parts will be described in detailhereinafter.

The power supply control unit 50 according to Modification 1 switchesthe state of power supply to the motor rotation sensor 46 and therotation detector 47 from the intermittently supplied state to thenormally supplied state when it determines that the motor rotationalspeed (rpm) becomes equal to or higher than a rotational speed ωt set inadvance, while the IG switch 62 is OFF and in the intermittentlysupplied state. The power supply control unit 50 is further configuredto make switching from the normally supplied state to the intermittentlysupplied state when it determines that the motor rotational speedbecomes lower than the set rotational speed ωt, in the normally suppliedstate after switching. In other words, while the IG switch 62 is OFF,when the driver steers the steering wheel 31 and the motor rotationalspeed becomes equal to or higher than the set rotational speed ωt, powerfrom the battery 61 is set in the normally supplied state so that achange in motor rotation position can be more reliably followed.

(Operation)

An operation according to Modification 1 of the first embodiment will bedescribed below with reference to FIG. 6.

Assume now that the IG switch 62 of the vehicle 1 changes from ON toOFF. Then, the power supply control unit 50 switches the state of powersupply from the battery 61 to the first and second rotation informationdetection function units 51 and 52 from the normally supplied state tothe intermittently supplied state.

More specifically, a switch (not illustrated) for switching between ONand OFF of power supplied from the battery 61 to the first and secondrotation information detection function units 51 and 52 is alternatelyturned on and off at certain intervals respectively set in advance forON and OFF states (1 [ms] for ON state and 99 [ms] for OFF state in theexample of FIG. 6), as illustrated in FIG. 6.

In this case, assume, for example, that the driver riding in a vehicleequipped with the idling stop function steers the steering wheel 31 torotate the motor rotating shaft 44 a after the IG switch 62 is turnedoff by this idling stop function, while waiting for the lights tochange.

Then, as illustrated in, for example, FIG. 6, when the motor rotationalspeed becomes equal to or higher than the set rotational speed cot (50[rpm] in the example of FIG. 6), the power supply control unit 50 makesswitching from the current, intermittently supplied state to thenormally supplied state. Referring to FIG. 6, a fine curved linerepresents the motor rotational speed and a bold straight linerepresents ON/OFF of the switch.

When the motor rotational speed becomes lower than the set rotationalspeed ωt, the power supply control unit 50 makes switching from thenormally supplied state to the intermittently supplied state.

With this operation, when steering is performed such that the motorrotational speed becomes the set rotational speed ωt or more while theIG switch 62 is OFF, the first and second counter units 471 c and 472 ccan count values according to changes of the first and second digitalrotation position signals in full operation in the normally suppliedstate, and the first memory unit 471 d and the second memory unit 472 dcan store the first count values Cs1 and Cc1 and the second count valuesCs2 and Cc2 in full operation.

Effects of Modification 1

(1) The motor drive control device 45 according to Modification 1 of thefirst embodiment switches power from the battery 61, from theintermittently supplied state to the continuously supplied state whenthe power supply control unit 50 detects a motor rotational speed of theelectric motor 44 equal to or higher than the rotational speed ωt set inadvance, while the IG switch 62 is OFF.

With this configuration, when the driver steers the steering wheel 31while the IG switch 62 is OFF, if the motor rotational speed becomesequal to or higher than the set rotational speed ωt upon this steering,switching is made from the intermittently supplied state to the normallysupplied state to allow full operation of the first and second rotationinformation detection function units 51 and 52. This allows morereliable measurement of an amount of change in motor rotation positionwhen the motor rotational speed becomes the set rotational speed ωt ormore.

Modification 2 of First Embodiment

Modification 2 of the first embodiment will be described below withreference to FIG. 7.

Modification 2 is different from the first embodiment in that in thefirst embodiment the power supply control unit 50 intermittentlysupplies power from the battery 61 to all constituent units of the firstand second rotation information detection function units 51 and 52 whilethe IG switch 62 is OFF, but in Modification 2 power is intermittentlysupplied to only some constituent units.

The same reference numerals as in the first embodiment denote the sameconstituent units, and a description thereof will be omitted asappropriate, while only different parts will be described in detailhereinafter.

The power supply control unit 50 according to Modification 2 isconfigured to intermittently supply power from the battery 61 toconstituent units marked with downward arrows and completely stopsupplying power to constituent units marked with no arrows, asillustrated in FIG. 7, while the IG switch 62 is OFF.

More specifically, the power supply control unit 50 according toModification 2 intermittently supplies power from the battery 61 to onlythe first and second rotation position information detection units 46 band 46 c, the first and second ADCs 471 a and 472 a, the first andsecond diagnosis units 471 b and 472 b, the first and second counterunits 471 c and 472 c, and the first and second memory units 471 d and472 d, while the IG switch 62 is OFF. These constituent units will alsobe abbreviated as “power supplied constituent units” hereinafter.

The power supply control unit 50 according to Modification 2 completelystops (cuts off) power supplied from the battery 61 to the first andsecond rotation angle calculation units 471 e and 472 e and the firstand second output determination units 471 f and 472 f, while the IGswitch 62 is OFF. These constituent units will also be abbreviated as“power stopped constituent units” hereinafter.

More specifically, in the power supply control unit 50 according toModification 2, switches (not illustrated) for turning on and off powersupplied from the battery 61 are individually provided for the powersupplied constituent units and the power stopped constituent units ofthe first and second rotation information detection function units 51and 52.

The power supply control unit 50 alternately turns on and off theswitches corresponding to the power supplied constituent units at apreset certain interval to intermittently supply power to the powersupplied constituent units, while the IG switch 62 is OFF.

Upon application of the configuration according to Modification 1, inthe intermittently supplied state, when the driver steers the steeringwheel 31 and the motor rotational speed becomes equal to or higher thana rotational speed ωt set in advance, the switches corresponding to thepower supplied constituent units are kept ON to switch the state ofpower supply to the power supplied constituent units from theintermittently supplied state to the normally supplied state. When themotor rotational speed lowers from the set rotational speed ωt or moreto less than the set rotational speed ωt, the state of power supply tothe power supplied constituent units is switched from the normallysupplied state to the intermittently supplied state.

The power supply control unit 50 keeps the switches corresponding to thepower stopped constituent units OFF to cut off power supplied to thepower stopped constituent units, while the IG switch 62 is OFF.

Effects of Modification 2

Modification 2 of the first embodiment has the following effects, inaddition to the effects of the first embodiment.

(1) In the motor drive control device 45 according to Modification 2,the power supply control unit 50 intermittently supplies power from thebattery 61 to the first and second ADCs 471 a and 472 a, the first andsecond rotation position information detection units 46 b and 46 c, thefirst and second diagnosis units 471 b and 472 b, the first and secondcounter units 471 c and 472 c, and the first and second memory units 471d and 472 d in the first and second rotation information detectionfunction units 51 and 52 and cuts off power supplied to the remainingconstituent units, while the IG switch 62 is OFF.

With this configuration, while the IG switch 62 is OFF, power can besupplied to only constituent units which need to be actuated in OFFstate (constituent units required to measure an amount of change inmotor rotation position) in addition to intermittent power supply, thusmore reliably cutting the power consumption in OFF state.

Modification 3 of First Embodiment

Modification 3 of the first embodiment will be described below.

Modification 3 is different from the first embodiment in thatModification 3 includes a first and a second MUXs (MUltipleXers) 471 gand 472 g located upstream of the first and second ADCs 471 a and 472 a,and monitoring potentials are input to the first and second ADCs 471 aand 472 a via the first and second MUXs 471 g and 472 g. Abnormalitydiagnosis of the first and second MUXs 471 g and 472 g and the first andsecond ADCs 471 a and 472 a is performed based on the A/D conversionresult of the monitoring potentials.

The same reference numerals as in the first embodiment denote the sameconstituent units, and a description thereof will be omitted asappropriate, while only different parts will be described in detailhereinafter.

The first and second rotation information detection units 47 a and 47 baccording to Modification 3 newly include the first and second MUXs 471g and 472 g, as illustrated in FIG. 8.

The first MUX 471 g includes pluralities of signal input terminals andselection signal input terminals and at least one output terminal (noneare illustrated), selects a signal to be output to the first ADC 471 afrom signals input to the plurality of input terminals, based on a firstselection signal SL1 from the first diagnosis unit 471 b, and outputsthe selected signal to the first ADC 471 a.

In Modification 3, the types of signals input to the first ADC 471 ainclude the first motor rotation position signal (sin θ1, cos θ1) outputfrom the first rotation position information detection unit 46 b, andfirst monitoring potential signals Vc11 to Vc1 n (n is a natural numberof 1 or more) for abnormality diagnosis of the first ADC 471 a outputfrom the first diagnosis unit 471 b. Therefore, the first MUX 471 gsequentially selects these signals in accordance with the firstselection signal SL1 and outputs them to the first ADC 471 a.

The first ADC 471 a according to Modification 3 converts analog signalssequentially input from the first MUX 471 g into digital signals andoutputs them to the downstream constituent units.

More specifically, the first ADC 471 a according to Modification 3converts the analog, first motor rotation position signal (sin θ1, cosθ1) input from the first MUX 471 g into the first digital rotationposition signal (sin θd1, cos θd1) and outputs it to each of the firstdiagnosis unit 471 b, the first counter unit 471 c, and the firstrotation angle calculation unit 471 e.

The first ADC 471 a according to Modification 3 further converts theanalog, first monitoring potential signals Vc11 to Vc1 n input from thefirst MUX 471 g into first digital potential signals Vcd11 to Vcd1 n asdigital, first monitoring potential signals and outputs them to thefirst diagnosis unit 471 b.

The first diagnosis unit 471 b according to Modification 3 includes afirst rotation information diagnosis unit 1471 and a first MUX/ADCdiagnosis unit 1472, as illustrated in FIG. 9A.

The first rotation information diagnosis unit 1471 serves as aconstituent unit including the same function as that of the firstdiagnosis unit 471 b according to the first embodiment. In other words,the first rotation information diagnosis unit 1471 diagnoses anabnormality of the first digital rotation position signal (sin θd1, cosθd1), based on equation (1) in the first embodiment, and outputs to eachof the first counter unit 471 c, the first memory unit 471 d, and thefirst output determination unit 471 f, “1” for the presence of anabnormality and “0” for the absence of an abnormality as a firstdiagnosis result flag DR1.

The first MUX/ADC diagnosis unit 1472 generates the first monitoringpotential signals Vc11 to Vc1 n from a voltage VCC applied from thebattery 61 and inputs the generated first monitoring potential signalsVc11 to Vc1 n to the input terminals of the first MUX 471 g.

The first MUX/ADC diagnosis unit 1472 further generates the firstselection signal SL1 for outputting the first motor rotation positionsignal (sin θ1, cos θ1) and the first monitoring potential signals Vc11to Vc1 n input to the input terminals of the first MUX 471 g to thefirst ADC 471 a while sequentially switching them using a preset orderand time interval and inputs the generated first selection signal SL1 tothe selection signal input terminal of the first MUX 471 g.

Note, however, that the first MUX/ADC diagnosis unit 1472 according toModification 3 inputs the first selection signal SL1, for outputting thefirst monitoring potential signals Vc11 to Vc1 n while sequentiallyswitching them, to the selection signal input terminal only onceimmediately after a change to ON every time the IG switch 62 changesfrom OFF to ON. While the IG switch 62 is subsequently kept ON, thefirst MUX/ADC diagnosis unit 1472 inputs to the selection signal inputterminal, the first selection signal SL1 for outputting the first motorrotation position signal (sin θ1, cos θ1) while alternately switchingthem.

The first MUX/ADC diagnosis unit 1472 compares each of the first digitalpotential signals Vcd11 to Vcd1 n input from the first ADC 471 a with acorresponding one of preset first comparison potentials Vct11 to Vct1 n,having the same suffix.

In this case, the first comparison potentials Vct11 to Vct1 n takevalues having their respective tolerances, and it is determined that noabnormality has occurred in the first MUX 471 g and the first ADC 471 awhen all the first digital potential signals Vcd11 to Vcd1 n fall withinthe tolerances (for example, values between the upper and lower limits)of the first comparison potentials Vct11 to Vct1 n. It is determinedthat an abnormality has occurred in the first MUX 471 g and the firstADC 471 a when at least one of the first digital potential signals Vcd11to Vcd1 n falls outside the tolerance.

When it is determined that no abnormality has occurred, the firstMUX/ADC diagnosis unit 1472 outputs “0” as a first ADC diagnosis resultflag DMA1 to each of the first counter unit 471 c, the first memory unit471 d, and the first output determination unit 471 f. When it isdetermined that an abnormality has occurred, the first MUX/ADC diagnosisunit 1472 outputs “1” as the first ADC diagnosis result flag DMA1 toeach of the first counter unit 471 c, the first memory unit 471 d, andthe first output determination unit 471 f.

The first counter unit 471 c and the first memory unit 471 d accordingto Modification 3 stop their operations when at least one of the firstdiagnosis result flag DR1 and the first ADC diagnosis result flag DMA1is “1”.

The first output determination unit 471 f according to Modification 3outputs the first diagnosis result flag DR1, the first ADC diagnosisresult flag DMA1, the first motor rotation angle θm1, and the firstcount values Cs1 and Cc1 to the controller 48 when the first diagnosisresult flag DR1 and the first ADC diagnosis result flag DMA1 are both“0”.

The first output determination unit 471 f stops outputting the firstmotor rotation angle θm1 and the first count values Cs1 and Cc1 to thecontroller 48 and outputs only the first diagnosis result flag DR1 andthe first ADC diagnosis result flag DMA1 to the controller 48, when atleast one of the first diagnosis result flag DR1 and the first ADCdiagnosis result flag DMA1 is “1”.

The second MUX 472 g and the second ADC 472 a according to Modification3 have the same configurations as those of the first MUX 471 g and thefirst ADC 471 a. In other words, since the operation details are thesame except that the second motor rotation position signal (sin θ2, cosθ2), the second digital rotation position signal (sin θd2, cos θd2), asecond selection signal SL2, second monitoring potential signals Vc21 toVc2 n, and second digital potential signals Vcd21 to Vcd2 n are used, adescription thereof will be omitted.

The second diagnosis unit 472 b according to Modification 3 includes asecond rotation information diagnosis unit 1473 and a second MUX/ADCdiagnosis unit 1474, as illustrated in FIG. 9B.

Since the second rotation information diagnosis unit 1473 has the sameconfiguration as that of the first rotation information diagnosis unit1471 except that the second digital rotation position signal (sin θd2,cos θd2) and the second diagnosis result flag DR2 are used, adescription thereof will be omitted.

The second MUX/ADC diagnosis unit 1474 has the same configuration asthat of the first MUX/ADC diagnosis unit 1472. In other words, since theoperation details are the same except that the second digital rotationposition signal (sin θd2, cos θd2), second digital potential signalsVcd21 to Vcd2 n, a second selection signal SL2, a second ADC diagnosisresult flag DMA2, and second comparison potentials Vct21 to Vct2 n areused, a description thereof will be omitted.

The second counter unit 472 c and the second memory unit 472 d accordingto Modification 3 stop their operations when at least one of the seconddiagnosis result flag DR2 and the second ADC diagnosis result flag DMA2is “1”.

The second output determination unit 472 f according to Modification 3outputs the second diagnosis result flag DR2, the second ADC diagnosisresult flag DMA2, the second motor rotation angle θm2, and the secondcount values Cs2 and Cc2 to the controller 48 when the second diagnosisresult flag DR2 and the second ADC diagnosis result flag DMA2 are both“0”.

The second output determination unit 472 f stops outputting the secondmotor rotation angle θm2 and the second count values Cs2 and Cc2 to thecontroller 48 and outputs only the second diagnosis result flag DR2 andthe second ADC diagnosis result flag DMA2 to the controller 48, when atleast one of the second diagnosis result flag DR2 and the second ADCdiagnosis result flag DMA2 is “1”.

The controller 48 according to Modification 3 determines the presence orabsence of an abnormality and identifies or estimates an abnormalityarea from the first diagnosis result flag DR1 and the first ADCdiagnosis result flag DMA1, and the second diagnosis result flag DR2 andthe second ADC diagnosis result flag DMA2 input from the first andsecond rotation information detection function units 51 and 52.

More specifically, the controller 48 according to Modification 3 canidentify abnormalities of the first MUX 471 g and the first ADC 471 a orthe second MUX 472 g and the second ADC 472 a when the first ADCdiagnosis result flag DMA1 or the second ADC diagnosis result flag DMA2is “1”.

When the first ADC diagnosis result flag DMA1 and the second ADCdiagnosis result flag DMA2 are “0,” and the first diagnosis result flagDR1 or the second diagnosis result flag DR2 is “1,” since an abnormalityhas occurred in the input motor rotation position signal, the controller48 can estimate that an abnormality has occurred in the first rotationposition information detection unit 46 b or the second rotation positioninformation detection unit 46 c, or the multipolar ring magnet 46 a.

(Operation)

An operation according to Modification 3 will be described below.

Assume now that the IG switch 62 changes from OFF to ON, and power issupplied from the battery 61 to the first and second rotationinformation detection function units 51 and 52 via the power supplycontrol unit 50 in the normally supplied state.

In this case, by using the normal ranges of use (0 to VCC) for the firstand second ADCs 471 a and 472 a as a reference, five types of the firstand second monitoring potential signals Vc11 to Vc15 and Vc21 to Vc25:“Vc11=Vc21=VCC*½,” “Vc12=Vc22=VCC*⅓,” “Vc13=Vc23=VCC*⅔,”“Vc14=Vc24=VCC”, and “Vc15=Vc25=0” are set.

In other words, the first monitoring potential signals Vc11 to Vc15 areinput from the first diagnosis unit 471 b to the input terminals of thefirst MUX 471 g, and the second monitoring potential signals Vc21 toVc25 are input from the second diagnosis unit 472 b to the second MUX472 g.

When the IG switch 62 changes from OFF to ON, the first and seconddiagnosis units 471 b and 472 b output to the first and second MUXs 471g and 472 g, the first and second selection signals SL1 and SL2 forselectively outputting the first and second monitoring potential signalsVc11 to Vc15 and Vc21 to Vc25.

More specifically, the first and second diagnosis units 471 b and 472 boutput to the first and second MUXs 471 g and 472 g, the first andsecond selection signals SL1 and SL2 for outputting the first and secondmonitoring potential signals Vc11 to Vc15 and Vc21 to Vc25 to the firstand second ADCs 471 a and 472 a while sequentially switching them at apreset time interval required in A/D conversion.

With this operation, the first MUX 471 g sequentially outputs the firstmonitoring potential signals Vc11 to Vc15 to the first ADC 471 a at apreset time interval, in accordance with the input first selectionsignal SL1. The first ADC 471 a sequentially converts the sequentiallyinput first monitoring potential signals Vc11 to Vc15 into the firstdigital potential signals Vcd11 to Vcd15 and sequentially outputs themto the first diagnosis unit 471 b.

Similarly, the second MUX 472 g outputs the second monitoring potentialsignals Vc21 to Vc25 to the second ADC 472 a at a preset time interval,in accordance with the input second selection signal SL2. The second ADC472 a sequentially converts the sequentially input second monitoringpotential signals Vc21 to Vc25 into the second digital potential signalsVcd21 to Vcd25 and sequentially outputs them to the second diagnosisunit 472 b.

The first diagnosis unit 471 b sequentially compares each of thesequentially input first digital potential signals Vcd11 to Vcd15 with acorresponding one of the first comparison potentials Vct11 to Vct15,having the same suffix, and generates a first ADC diagnosis result flagDMA1 based on this comparison result. Similarly, the second diagnosisunit 472 b sequentially compares each of the sequentially input seconddigital potential signals Vcd21 to Vcd25 with a corresponding one of thesecond comparison potentials Vct21 to Vct25 and generates a second ADCdiagnosis result flag DMA2 based on this comparison result.

The first diagnosis unit 471 b generates the first ADC diagnosis resultflag DMA1 of “0” when it determines that all the first digital potentialsignals Vcd11 to Vcd15 fall within the tolerances indicated by the firstcomparison potentials Vct11 to Vct15, and generates the first ADCdiagnosis result flag of “1” when it determines that at least one ofthese signals falls outside the tolerance.

The second diagnosis unit 472 b generates the second ADC diagnosisresult flag DMA2 of “0” when it determines that all the second digitalpotential signals Vcd21 to Vcd25 fall within the tolerances indicated bythe second comparison potentials Vct21 to Vct25, and generates thesecond ADC diagnosis result flag of “1” when it determines that at leastone of these signals falls outside the tolerance.

The first and second diagnosis units 471 b and 472 b output thegenerated first and second ADC diagnosis result flags DMA1 and DMA2 tothe first and second counter units 471 c and 472 c, the first and secondmemory units 471 d and 472 d, and the first and second outputdetermination units 471 f and 472 f.

The first and second counter units 471 c and 472 c and the first andsecond memory units 471 d and 472 d stop their subsequent operationswhen the first and second ADC diagnosis result flags DMA1 and DMA2 are“1”, and these units perform their normal operations subsequently whenthese flags are “0”.

When the first and second ADC diagnosis result flags DMA1 and DMA2 are“1”, the first and second output determination units 471 f and 472 foutput the first and second diagnosis result flags DR1 and DR2 and thefirst and second ADC diagnosis result flags DMA1 and DMA2 to thecontroller 48. The first and second output determination units 471 f and472 f stop their subsequent processing for outputting the first andsecond motor rotation angles θm1 and θm2, the first count values Cs1 andCc1, and the second count values Cs2 and Cc2.

When the first and second ADC diagnosis result flags DMA1 and DMA2 are“0”, the first and second output determination units 471 f and 472 foutput the first and second diagnosis result flags DR1 and DR2 and thefirst and second ADC diagnosis result flags DMA1 and DMA2 to thecontroller 48 and perform their normal output operations subsequently.

The first ADC 471 a and the second ADC 472 a correspond to an A/Dconverter, the first MUX/ADC diagnosis unit 1472 and the second MUX/ADCdiagnosis unit 1474 correspond to an A/D converter diagnosis unit, andthe first MUX 471 g and the second MUX 472 g correspond to a monitoringpotential signal input unit.

Effects of Modification 3

Modification 3 of the first embodiment has the following effects, inaddition to the effects of the first embodiment.

(1) In the motor drive control device 45 according to Modification 3,the first and second rotation information detection function units 51and 52 include the first and second ADCs 471 a and 472 a which convertthe analog, first and second motor rotation position signals into thedigital, first and second digital rotation position signals, the firstand second MUXs 471 g and 472 g which input the analog, first and secondmonitoring potential signals Vc11 to Vc1 n and Vc21 to Vc2 n to thefirst and second ADCs 471 a and 471 b, and the first and second MUX/ADCdiagnosis units 1472 and 1474 which compare the first and second digitalpotential signals Vcd11 to Vcd1 n and Vcd21 to Vcd2 n obtained byconversion into digital signals by the first and second ADCs 471 a and472 a with the preset first and second comparison potentials Vct11 toVct1 n and Vct21 to Vct2 n to diagnose abnormalities of the first andsecond ADCs 471 a and 471 b and the first and second MUXs 471 g and 472g based on the comparison result.

With this configuration, the first and second ADCs 471 a and 471 b andthe first and second MUXs 471 g and 472 g can be diagnosed as abnormal,based on the first and second digital potential signals Vcd11 to Vcd1 nand Vcd21 to Vcd2 n obtained by A/D-converting the analog, the first andsecond monitoring potential signals Vc11 to Vc1 n and Vc21 to Vc2 nusing the first and second ADCs 471 a and 472 a.

With this operation, abnormalities of the first ADC 471 a and the firstMUX 471 g, and the second ADC 472 a and the second MUX 472 g can berespectively identified.

Modification 4 of First Embodiment

Modification 4 of the first embodiment will be described below.Modification 4 is different from the first embodiment in that thecounter function units of the first and second counter units 471 c and472 c are dualized, and the count values obtained by the dualizedcounter function units are compared with each other to allow the firstand second counter units 471 c and 472 c to diagnose their ownabnormalities. Another difference from the first embodiment lies in thattwo address areas are set in each of the first and second memory units471 d and 472 d, the count value obtained by one of the dualized counterfunction units of the first and second counter units 471 c and 472 c isstored in one of the two address areas of each memory unit while theother count value is stored in the other address area, and these storedcount values are compared between the areas to allow the first andsecond memory units 471 d and 472 d to diagnose their own abnormalities.

The same reference numerals as in the first embodiment denote the sameconstituent units, and a description thereof will be omitted asappropriate, while only different parts will be described in detailhereinafter.

The first counter unit 471 c according to Modification 4 includes afirst counter 1475, a second counter 1476, and a first countercomparison unit 1477, as illustrated in FIG. 10A.

The first and second counters 1475 and 1476 count the values ofsynchronously input sin θd1 and cos θd1 for each of their quadrants andoutput first sin count values Cs11 and Cs12 and first cos count valuesCc11 and Cc12 to the first counter comparison unit 1477 as the countvalues.

The first counter comparison unit 1477 compares the count values Cs11and Cc11 input from the first counter 1475 with the count values Cs12and Cc12 input from the second counter 1476. It is determined that noabnormality has occurred in the count values and “0” is set as a firstcounter diagnosis result flag DC1 when “Cs11=Cs12” and “Cc11=Cc12” hold,and that an abnormality has occurred in the count values and “1” is setas such a flag when they do not hold. The first counter comparison unit1477 outputs the set first counter diagnosis result flag DC1 to each ofthe first memory unit 471 d and the first output determination unit 471f.

The first counter comparison unit 1477 further outputs the first sincount values Cs11 and Cs12 and the first cos count values Cc11 and Cc12to the first memory unit 471 d when the first counter diagnosis resultflag DC1 is “0” and stops outputting them when the first counterdiagnosis result flag DC1 is “1”.

The first memory unit 471 d according to Modification 4 includes a firstmemory area 1478, a second memory area 1479, and a first memorycomparison unit 1480, as illustrated in FIG. 10A.

The first memory area 1478 serves as a memory area which stores thefirst sin count value Cs11 and the first cos count value Cc11.

The second memory area 1479 serves as a memory area which stores thefirst sin count value Cs12 and the first cos count value Cc12.

In Modification 4, the first memory unit 471 d is configured to invertthe logic of the first sin count value Cs12 and the first cos countvalue Cc12 and store them in the second memory area 1479. In this case,the count values are logically inverted and stored to allow thedownstream, first memory comparison unit 1480 to detect a memoryfixation abnormality as well.

The first memory comparison unit 1480 determines whether or not thefirst sin count value Cs11 and the first cos count value Cc11 stored inthe first memory area 1478 are equal to the first sin count value Cs12and the first cos count value Cc12 logically inverted and stored in thesecond memory area 1479. More specifically, the first memory comparisonunit 1480 determines whether or not the former and latter count valuesare equal after returning the inverted logic to the original state. “0”is set as a first memory diagnosis result flag DM1 when these countvalues are totally equal, and “1” is set as such a flag when they aredifferent. The set first memory diagnosis result flag DM1 is output tothe first output determination unit 471 f.

The first memory unit 471 d according to Modification 4 is configured tostop the operation when the first counter diagnosis result flag DC1input from the first counter unit 471 c is “1”.

The second counter unit 472 c according to Modification 4 includes athird counter 1481, a fourth counter 1482, and a second countercomparison unit 1483, as illustrated in FIG. 10B.

The third counter 1481, the fourth counter 1482, and the second countercomparison unit 1483 have the same configurations as those of the firstcounter 1475, the second counter 1476, and the first counter comparisonunit 1477. In other words, since the operation details are the sameexcept that the sin θd2 and cos θd2, second sin count values Cs21 andCs22, second cos count values Cc21 and Cc22, and a second counterdiagnosis result flag DC2 are used, a description thereof will beomitted.

The second memory unit 472 d according to Modification 4 includes athird memory area 1484, a fourth memory area 1485, and a second memorycomparison unit 1486, as illustrated in FIG. 10B.

The third memory area 1484, the fourth memory area 1485, and the secondmemory comparison unit 1486 have the same configurations as those of thefirst memory area 1478, the first memory area 1479, and the first memorycomparison unit 1480. In other words, since the operation details arethe same except that the second sin count values Cs21 and Cs22, thesecond cos count values Cc21 and Cc22, and the second counter diagnosisresult flag DC2 are used, a description thereof will be omitted.

The first output determination unit 471 f according to Modification 4outputs the first diagnosis result flag DR1, the first counter diagnosisresult flag DC1, and the first memory diagnosis result flag DM1 to thecontroller 48 when at least one of these diagnosis result flags DR1,DC1, and DM1 is “1”. Subsequently, the first output determination unit471 f stops processing for outputting the first motor rotation angleθm1, the first sin count values Cs11 and Cs12, and the first cos countvalues Cc11 and Cc12 to the controller 48.

The first output determination unit 471 f according to Modification 4outputs the first diagnosis result flag DR1, the first counter diagnosisresult flag DC1, and the first memory diagnosis result flag DM1 to thecontroller 48 when all these diagnosis result flags DR1, DC1, and DM1are “0”. Subsequently, the first output determination unit 471 fperforms processing for outputting these diagnosis result flags DR1,DC1, and DM1, the first motor rotation angle θm1, the first sin countvalues Cs11 and Cs12, and the first cos count values Cc11 and Cc12 tothe controller 48.

The second output determination unit 472 f according to Modification 4has the same configuration as that of the first output determinationunit 471 f according to Modification 3. In other words, since theoperation details are the same except that the second diagnosis resultflag DR2, the second counter diagnosis result flag DC2, the secondmemory diagnosis result flag DM2, the second motor rotation angle θm2,the second sin count values Cs21 and Cs22, and the second cos countvalues Cc21 and Cc22 are used, a description thereof will be omitted.

The controller 48 according to Modification 4 can identify, based on thefirst counter diagnosis result flag DC1 and the first memory diagnosisresult flag DM1 from the first rotation information detection functionunit 51, an abnormality of the first counter unit 471 c when the firstcounter diagnosis result flag DC1 is “1” and an abnormality of the firstmemory unit 471 d when the first memory diagnosis result flag DM1 is“1”.

The controller 48 according to Modification 4 can also identify, basedon the second counter diagnosis result flag DC2 and the second memorydiagnosis result flag DM2 from the second rotation information detectionfunction unit 52, an abnormality of the second counter unit 472 c whenthe second counter diagnosis result flag DC2 is “1” and an abnormalityof the second memory unit 472 d when the second memory diagnosis resultflag DM2 is “1”.

(Operation)

An operation according to Modification 4 will be described below.

Assume now that the first and second digital rotation position signals(sin θd1, cos θd1) and (sin θd2, cos θd2) are input to the first andsecond counter units 471 c and 472 c.

Then, the first and second counters 1475 and 1476 of the first counterunit 471 c count sin θd1 and cos θd1 for each of their quadrants andoutput the first sin count values Cs11 and Cs12 and the first cos countvalues Cc11 and Cc12 to the first counter comparison unit 1477.

The first counter comparison unit 1477 compares the respective countvalues with each other to determine whether or not “Cs11=Cs12” and“Cc11=Cc12” hold and diagnoses these count values as normal when itdetermines that they hold and as abnormal when it determines that theydo not hold. The first counter comparison unit 1477 outputs the firstcounter diagnosis result flag DC1 having a value according to thediagnosis result to each of the first memory unit 471 d and the firstoutput determination unit 471 f. In this case, when these count valuesare normal, the first counter comparison unit 1477 further outputs thefirst sin count values Cs11 and Cs12 and the first cos count values Cc11and Cc12 to the first memory unit 471 d.

The first memory unit 471 d stores the input first sin count value Cs11and first cos count value Cc11 in the first memory area 1478, while itinverts the logic of the input first sin count value Cs12 and first coscount value Cc12 and stores them in the second memory area 1479.

The first memory comparison unit 1480 compares the first sin count valueCs11 and the first cos count value Cc11 stored in the first memory area1478 with the first sin count value Cs12 and the first cos count valueCc12 stored in the second memory area 1479 after returning the logic tothe original state. The first memory comparison unit 1480 determineswhether or not “Cs11=Cs12” and “Cc11=Cc12” hold and diagnoses thesecount values as normal when it determines that they hold and as abnormalwhen it determines that they do not hold. The first memory comparisonunit 1480 outputs the first memory diagnosis result flag DM1 having avalue according to the diagnosis result to the first outputdetermination unit 471 f.

Since the operations of the second counter unit 472 c and the secondmemory unit 472 d are the same as those of the first counter unit 471 cand the first memory unit 471 d except that different signals are used,a description thereof will be omitted.

The controller 48 determines whether or not an abnormality has occurredin the first counter unit 471 c and the first memory unit 471 d, basedon the first counter diagnosis result flag DC1 and the first memorydiagnosis result flag DM1 from the first rotation information detectionfunction unit 51. Thus, the controller 48 can identify an abnormality ofthe first counter unit 471 c when the first counter diagnosis resultflag DC1 is “1” and an abnormality of the first memory unit 471 d whenthe first memory diagnosis result flag DM1 is “1”.

The controller 48 also determines whether or not an abnormality hasoccurred in the second counter unit 472 c and the second memory unit 472d, based on the second counter diagnosis result flag DC2 and the secondmemory diagnosis result flag DM2 from the second rotation informationdetection function unit 52. Thus, the controller 48 can identify anabnormality of the second counter unit 472 c when the second counterdiagnosis result flag DC2 is “1” and an abnormality of the second memoryunit 472 d when the second memory diagnosis result flag DM2 is “1”.

The first and second counters 1475 and 1476 and the third and fourthcounters 1481 and 1482 correspond to a change amount measurement unit,and the first and second memory areas 1478 and 1479 and the third andfourth memory areas 1484 and 1485 correspond to a change amount storageunit.

The first and second counter comparison units 1277 and 1480 and thefirst and second memory comparison units 1480 and 1486 correspond to ameasurement abnormality diagnosis unit.

Effects of Modification 4

Modification 4 has the following effects, in addition to the effects ofthe first embodiment.

(1) In the motor drive control device 45 according to Modification 4,the first and second counters 1475 and 1476 and the third and fourthcounters 1481 and 1482 of the first and second counter units 471 c and472 c measure amounts of change in rotation position (the first sincount values Cs11 and Cs12, the first cos count values Cc11 and Cc12,the second sin count values Cs21 and Cs22, and the second cos countvalues Cc21 and Cc22) of the electric motor 44 based on the first andsecond motor rotation position signals detected by the first and secondrotation position information detection units 46 b and 46 c. The firstand second counter comparison units 1277 and 1480 of the first andsecond counter units 471 c and 472 c diagnose abnormalities of the firstand second counter units 471 c and 472 c.

The first and second memory units 471 d and 472 d store the amounts ofchange measured by the first and second counters 1475 and 1476 and thethird and fourth counters 1481 and 1482 in the first and second memoryareas 1478 and 1479 and the third and fourth memory areas 1484 and 1485.The first and second memory comparison units 1480 and 1486 of the firstand second memory units 471 d and 472 d diagnose abnormalities of thefirst and second memory units 471 d and 472 d.

The first and second output determination units 471 f and 472 f outputthe amounts of change and the abnormality diagnosis results (the firstand second counter diagnosis result flags DC1 and DC2 and the first andsecond memory diagnosis result flags DM1 and DM2) to the controller 48.

With this configuration, the first and second counter units 471 c and472 c and the first and second memory units 471 d and 472 d canindividually diagnose their own abnormalities, which can thus beindividually identified.

In Modification 4, since the device is configured to invert the logic ofthe respective count values and store them in the second memory area1479 and the fourth memory area 1485, when a fixation abnormality hasoccurred in any memory area, this state can be detected as anabnormality.

Other Modifications

(1) In the first embodiment and each Modification, two systems ofrotation information detection function units are used, but the presentinvention is not limited to this configuration, and three or moresystems of rotation information detection function units may also beused.

(2) In the first embodiment and each Modification, the motor rotationsensor 46 is implemented as a magnetic sensor, but the present inventionis not limited to this configuration, and it may also be implemented asan optical sensor.

(3) In the first embodiment and each Modification, the device isconfigured to, when an abnormality occurs, output only various diagnosisresult flags to the controller 48, which identifies a rotationinformation detection function unit or each constituent unit having theabnormality, based on these diagnosis result flags, but the presentinvention is not limited to this configuration. For example, the devicemay be configured to, even when an abnormality occurs, output thecalculated motor rotation angles or the measured count values to thecontroller 48, which may compare the motor rotation angles or the countvalues with each other between the respective systems to perform dualabnormality diagnosis.

(4) In Modification 3 of the first embodiment, the device is configuredto perform abnormality diagnosis of the MUXs and the ADCs only onceevery time the IG switch 62 changes from OFF to ON, but the presentinvention is not limited to this configuration, and it may be configuredto continuously or periodically perform such abnormality diagnosis evenin ON state.

(5) In Modification 3 of the first embodiment, a plurality of types ofmonitoring potentials are set, but the present invention is not limitedto this configuration, and only one type of monitoring potential may beset.

(6) Each of Modifications 1 to 4 of the first embodiment is not limitedto an independent configuration, and they may be used in anycombination.

(7) In the first embodiment and each Modification, the rotation positioninformation input to each counter unit is defined as (sin θ, cos θ), butthe present invention is not limited to this configuration as long asany rotation position information is used. Rotation position informationobtained by angle calculation processing, for example, may be used.

(8) In Modification 1 of the first embodiment, in processing (to bereferred to as “first determination processing” hereinafter) fordetermining whether or not the motor rotational speed has become equalto or higher than a set rotational speed and processing (to be referredto as “second determination processing” hereinafter) for determiningwhether or not the motor rotational speed has become lower than the setrotational speed while the IG switch 62 is OFF, a common set rotationalspeed cot is used, but the present invention is not limited to thisconfiguration. Different set rotational speeds may be used in the firstdetermination processing and the second determination processing, suchas using a first set rotational speed ωt1 in the first determinationprocessing and a second set rotational speed ωt2 different from thefirst set rotational speed ωt1 in the second determination processing.

(9) In the first embodiment and each Modification, each of the firstrotation position information detection unit 46 b and the secondrotation position information detection unit 46 c includes two magneticdetection elements which detect magnetic signals out of phase with eachother, but the present invention is not limited to this configuration,and three or more magnetic detection elements may be used.

(10) In the first embodiment and each Modification, the presentinvention is applied to a column-assist electric power steering deviceby way of example, but the present invention is not limited to thisconfiguration, and the present invention is also applicable to, forexample, a rack- or pinion-assist electric power steering device.

(11) In the first embodiment and each Modification, the presentinvention is applied to a steering assist motor for an electric powersteering device byway of example, but the present invention is notlimited to this configuration, and the present invention is alsoapplicable to, for example, other vehicle-mounted motors such as a motorfor a power window device. Besides the vehicle-mounted motors, thepresent invention is also applicable to motors mounted in other devices.

This application claims priority based on Japanese Patent ApplicationNo. 2016-097215 (filed on May 13, 2016), the contents of which areincorporated by reference herein in its entirety.

While the present invention has been described above with reference toonly a limited number of embodiments, the scope of claims is not limitedthereto, and modifications to the embodiments based on theaforementioned disclosure will be apparent to those skilled in the art.

REFERENCE SIGNS LIST

-   1 . . . vehicle-   3 . . . electric power steering device-   44 . . . electric motor-   45 . . . motor drive control device-   46 . . . motor rotation sensor-   47 . . . rotation detector-   48 . . . controller-   49 . . . motor drive circuit-   50 . . . power supply control unit-   51 . . . first rotation information detection function unit-   52 . . . second rotation information detection function unit-   61 . . . battery-   62 . . . IG switch-   46 a . . . multipolar ring magnet-   46 b . . . first rotation position information detection unit-   46 c . . . second rotation position information detection unit-   47 a . . . first rotation information detection unit-   47 b . . . second rotation information detection unit-   471 a, 472 a . . . first and second ADCs-   471 b, 472 b . . . first and second diagnosis units-   471 c, 472 c . . . first and second counter units-   471 d, 472 d . . . first and second memory units-   471 e, 472 e . . . first and second rotation angle calculation units-   471 f, 472 f . . . first and second output determination units-   471 g, 472 g . . . first and second MUXs-   1471, 1473 . . . first and second rotation information diagnosis    units-   1472, 1474 . . . first and second MUX/ADC diagnosis units-   1475, 1476 . . . first and second counters-   1477, 1483 . . . first and second counter comparison units-   1481, 1482 . . . third and fourth counters-   1478, 1479 . . . first and second memory areas-   1480, 1486 . . . first and second memory comparison units-   1484, 1485 . . . third and fourth memory areas

The invention claimed is:
 1. A motor drive control device comprising: anannular or disk-shaped magnet placed on a motor rotating shaft of anelectric motor to be rotatable in synchronism with the motor rotatingshaft and includes at least two different magnetic poles arrangedalternately in a circumferential direction; at least two systems ofrotation information detection function units each including a rotationposition information detection unit configured to detect a magnetic fluxof the magnet which changes depending on a rotation position of themotor rotating shaft as rotation position information, a motor rotationangle calculation unit configured to calculate a motor rotation anglebased on the rotation position information detected by the rotationposition information detection unit, a rotation position informationdiagnosis unit configured to diagnose an abnormality of the rotationposition information detected by the rotation position informationdetection unit, and a rotation change amount measurement unit configuredto measure an amount of change in the rotation position of the electricmotor; and a motor drive control unit configured to control driving ofthe electric motor based on the motor rotation angle output from the atleast two systems of the rotation information detection function units,wherein the rotation position information detection unit includes aplurality of sensor elements configured to detect magnetic signals outof phase with each other as the rotation position information, theelectric motor is configured to apply a steering assist force to asteering shaft of a vehicle equipped with the motor drive controldevice, the motor drive control device is configured to supply powerfrom a battery of the vehicle to the at least two systems of therotation information detection function units even while an ignitionswitch is OFF, the rotation change amount measurement unit is configuredto continuously measure the amount of change in the rotation positioneven while the ignition switch is OFF, the rotation change amountmeasurement unit includes a change amount measurement unit configured tomeasure an amount of change in the rotation position of the electricmotor based on the rotation position information detected by therotation position information detection unit, a change amount storageunit configured to store the amount of change measured by the changeamount measurement unit, and a measurement abnormality diagnosis unitconfigured to diagnose an abnormality of the change amount measurementunit and the change amount storage unit, the motor drive control unit isconfigured to, when the rotation position information diagnosis unitdiagnoses at least one of the at least two systems of the rotationinformation detection function units as abnormal, control driving of theelectric motor based on the motor rotation angle output from another ofthe rotation information detection function units that is normal, themotor drive control unit is configured to calculate a steering anglethat is a rotation angle of the steering shaft based on the amount ofchange in the rotation position measured by the rotation change amountmeasurement unit when the ignition switch changes from OFF to ON, andcalculate the steering angle based on the motor rotation angle while theignition switch is subsequently kept ON, and control driving of theelectric motor based on the calculated steering angle, and the motordrive control unit is configured to, when the measurement abnormalitydiagnosis unit diagnoses at least one of the at least two systems of therotation information detection function units as abnormal, calculate thesteering angle based on the amount of change output from another of therotation information detection function units that is normal.
 2. Themotor drive control device according to claim 1, further including apower supply control unit configured to intermittently supply power fromthe battery of the vehicle to the at least two systems of the rotationinformation detection function units while the ignition switch is OFF.3. The motor drive control device according to claim 2, wherein thepower supply control unit is configured to make switching from a statein which the power is intermittently supplied from the battery to astate in which the power is continuously supplied from the battery, whena motor rotational speed of the electric motor that is not less than arotational speed set in advance is detected while the ignition switch isOFF.
 4. The motor drive control device according to claim 2, wherein thepower supply control unit is configured to intermittently supply thepower from the battery to the rotation position information detectionunit, the rotation position information diagnosis unit, and the rotationchange amount measurement unit in each of the at least two systems ofthe rotation information detection function units and cut off the powersupplied to other constituent units, while the ignition switch is OFF.5. The motor drive control device according to claim 1, wherein each ofthe at least two systems of the rotation information detection functionunits includes an A/D converter configured to convert an analog signalcorresponding to the rotation position information into a digitalsignal, a monitoring potential signal input unit configured to input ananalog monitoring potential signal to the A/D converter, and an A/Dconverter diagnosis unit configured to compare the monitoring potentialsignal converted into a digital signal by the A/D converter with apreset comparison potential to diagnose an abnormality of the A/Dconverter based on the comparison result.
 6. An electric power steeringdevice including the motor drive control device according to claim
 1. 7.A vehicle including the electric power steering device according toclaim 6.